Electric circuit breaker



Feb. 17,, 1948.

A. c. BOISSEAU ETAL 2.436,190

ELECTRIC CIRCUIT BREAKER Filed Nov. 7, 1944 2 Sheets-Sheet 1 Fig}.

Insulation 44 5 0 I Inventors:

Alexander C. Boisseau, J 2 9 Rahah E. Sold,

- Patented Feb. 17, 1948 UNITED STATES PATENT OFFICE ELECTRIC cmcurrBREAKER 7 Application November 7, 1944, Serial No. 562,296

8 Claims. (Cl. 200 -82) Our invention relates to electric circuit breakers and more particularly to operating mechanisms for electric circuitbreakers of the' fluid operated type. Specifically, our invention is animprovement on the circuit breaker operating system disclosed andclaimed in United States Letters Patent 2,315,991, 'I'humin, grantedApril 6, 1943, and assigned to the same assignee as the presentapplication.

Fluid operated circuit breakers have been used quite extensively withinthe last several years, particularly since the advent of the air blastcircuit breakers. Since an air blast circuit breaker requires a sourceof air under pressure, it is usualiy advantageous to also utilize thissource of air as the source of energy for operating the circuit breaker.

Heretofore, operating mechanisms for fluid p: erated circuit breakersand particularly fluid operated, fluid blast circuit breakers have beenvery complicated and expensive.

It is an object of the present invention to provide a new and improvedoperating mechanism for electric circuit breakers.

it is another object of our invention to provide an operating mechanismfor electric circuit breakers which is simple and compact and requiresonly a fraction of the space and material required by the operatingmechanisms used heretofore.

It is another object of our invention to provide an operating mechanismfor electric circuit breakers which is simple and compact and whichfurthermore provides all the functions of retarding, accelerating andoperating associated apparatus such as switches, blast valves, and thelike.

Further objects and advantages of our inven tion will become apparent asthe following description proceeds and the features of novelty whichcharacterize our invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of our invention, reference may be had to theaccompanying drawings in which Fig. 1 is a schematic diagram, partly insection, of an electric circuit breaker and operating mechanism thereforwith the circuit breaker shown in the closed circuit position; Fig. 2 isa view similar to Fig. 1 showing the circuit breaker in the open circuitposition; Fig. 3 is an elevational view, partly in section, of acommercial embodiment of our invention schematically shown in Figs. 1and 2 with minor modiflcations; and Fig. 4 is a portion of theembodiment shown in Fig. 3 viewed from the left hand side. I

Although our invention is particularly applicable to polyphase circuitbreakers, as will become apparent from the description of Figs. 3 and 4included hereinafter, we have illustrated our invention schematically inFigs. 1 and 2, as applied to a circuit breaker I, which is illustratedas a single phase circuit breaker of the cross gas blast type. Circuitbreaker I. comprises a stationary contact 2 and a movable contact 3arranged to be operated so as to draw an arc in arc chute 8, Contacts 2and 3 are arranged to be connected with suitable line terminalsschematically shown at 5 and '8, respectively. The fixed contact 2 isprovided with spring pressed contact fingers l and longer arcing contactfingers 8, while movable contact 3 is provided with an arcing tip 9 sothat when the contacts separate an arc occurs between arcing fingers 8and arcing tip 9. Immediately after the separation of the contacts oneterminal of the arc is transferred by a blast of fluid, such as air,flowing in conduit 1-, from contact fingers 8 to a contact I l which isprovided with a tip of arc resistantmetal. The fluid blast from conduitl0 upon opening of the circuit breaker l drives the arc into the arcchute 4 against the edges of a plurality of partitions or baflles i2,

which partitions are transverse to the arc gap and the ends of whichextend close to the path of movement of the arcing tip 9 of movablecontact 3. The circuit breaker is illustrated by way oi example onlyorder to describe our new and improved operating and controlarrangement. This circuit breaker i, briefly described above,

is not our invention but is described and claimed in United StatesLetters Patent 2,28%,842, granted June 21, 1942, and assigned to thesame assignee as the present application.

In view of the fact that we have illustrated ch":- cuit breaker i as afluid blast circuit breaker of the cross air blast type, it is necessaryto provide a source of fluid under pressure which is illustrated at l3.Conduit ID is connected to source I3 through a-blast valve l4 having areciprocally movable valve member l5 fastened to a suitable valve stemii. A spring I! normally biases valve member l5 to the closed positionindicated in Fig. 1.

Since a source of air or fluid under pressure I3 is necessary for airblast circuit breaker I, it is desirable to utilize this same source offluid under pressure to produce the energy for operating the circuitbreaker to the open and closed positions. In accordance with ourinvention we have provided a simple and compact fluid operated operatingmechanism generally indicated at l8. Operating mechanism l3 includes afluid motor comprising a circuit breaker opening piston l9 and a circuitbreaker closing piston 20 rigidly interconnected by a rack 2|. Piston I3is reciprocal in a cylinder 22 while piston 20 is reciprocal in cylinder23. Preferably these cylinders 22 and 23 are arranged as one continuouscylinder with a discontinuous portion so that a pinion 24 fixedlymounted on a rotatable shaft 25 may engage rack 2|. With thisarrangement the rectilinear motion of the pistons of the fluid motor istranslated into rotary motion of shaft 25.-

Cylinder 22 is connected to source l3 through schematically illustratedcircuit breaker opening valve 26 and conduit 21. Similarly, cylinder 23is connected to source l3 through circuit breaker closing valve 23 alsoschematically shown, and conduit 29. The circuit breaker opening andclosing valves 26 and 23, respectively, may be controlled in anysuitable manner well known to those skilled in the art and no furtherdiscussion thereof will be included herewith.

In order to provide accurate speed control of the fluid motor includingpistons l9 and 20, we have provided another set of pistons 30 and 3|rigidly interconnected by a rack 32, which rack also engages pinion 24.Pistons 30 and 3| are mounted in cylinders 33 and 34, respectively,which like cylinders 22 and 23 are preferably arranged as one continuouscylinder, parallel with the continuous cylinder comprising cylinders 22and 23. It will be obvious that with this arrangement, whenever pistons83 and 2d are moved to the left, as viewed in Fig. 1, pistons 30 and. 3|will be moved to the right by virtue of pinion 23, whose teeth engagewith both racks 2| and 32.

Pistons 3B and 3| provide a very desirable means for controlling thespeed of operation of the operating mechanism is during an operatingstroke of the circuit breaker and eliminate the requirement of anyseparate dashpots or retarding devices as was required in prior artarrangements. Pistons 30 and 3| therefore act as buffers or dashpots toretard the operating mechanism in any desired manner. A suitable springloaded check valve 35 controls a passageway 36 between cylinders 22 and33. Similarly, a spring loaded check valve 31 controls a passageway 38interconnecting cylinders 23 and 34. The size of pas- 'sageways 36 and38 and the spring loading of check valves 35 and 31 are arranged so asto charge the associated cylinders 33 and 36 during operating strokes ofthe circuit breaker to give the desired speed control as will be broughtout in greater detail hereinafter. In order to improve the speedcontrol, cylinder 33 is provided with a needle valve 39 leading toatmosphere and cylinder 34 is provided with a needle valve as, also leading to' atmosphere. Although in Figs. 1 and 2 we have illustratedpistons l3 and 23 as being larger than pistons 33 and 3!, it should beunderstood that these pistons may all be the same size as shown in Fig.3 if desired.

From the description of the operating mechanism i8 above it is obviousthat the fluid motor produces rotation of shaft 25 and it is obviousthat shaft 25 may be connected to one or more sets of relatively movablecontacts to produce relative movement between said contacts.

Rigidly fastened to shaft 25 and rotatable therewith is'a crank arm 4|.Preferably the free end of crank arm 4| is pivotally connected asinrollers 45, arranged two on either side of movable contact 3.

It will be observed that link 43 and crank arm 4| are arranged so as toprovide a toggle arrangement so that with the circuit breaker in theclosed position shown in Fig. 1, this toggle is in an overcenterposition so that any force applied to the contacts tending to open thecircuit breaker will have no effect, and fluid under pressure must beprovided in cylinder 22 in order to rotate crank arm 4| slightly andmove the toggle out of its locking position, or other means for rotatingcrank arm 4| must be provided.

It will be observed that when the circuit breaker is in the openposition indicated in Fig. 2, link 43 and crank arm 4| again form anover-center toggle arrangement with the goose-neck 43" fitting aroundshaft 25. Any force applied to movable contact 3 tending to close thecircuit breaker will be inefiective and the breaker is efiectivelylocked in the open position requiring movement of piston 1 20 to releasethe locking means. The rotation of shaft 25 from open to closed positionis somewhat more than With our improved operating mechanism the blastvalve it can readily be operated in response to relative movement of thecontacts merely by providing a cam 66 on shaft 25 rotatable with shaft25. Cam 3G- engages with a roller Elli -mounted on a bell crank 53pivotally mounted at 69. Bell crank 38 has an extension 48 engageablewith blast valve stem It. Upon rotation of haft 25 in acounter-clockwise direction as viewed in Fig. 1, blast valve i3 isopened to provide a blast of fluid under pressure adjacent rela= tivelymovable contacts 2 and 3 before these contacts separate sufficiently todraw an are therebetween. It should be noted that the lift of the blastvalve during the opening stroke occurs while the locking toggle is beingreleased and before force is applied to accelerate moving contactblades, thereby maintaining the force required to open the breaker at aminimum.

It should be understood that cutofi switches and the like can becontrolled very simply with our new and improved operating mechanismmerely by providing additional cams on shaft 25.

The operation of the arrangement disclosed in Figs. 1 and 2 will beobvious to those skilled in the art in view of the detailed descriptionincluded above. If the circuit breaker opening valve 26 is opened, fluidunder pressure enters cylinder 22 forcing piston is to the left, asviewed in Fig. 1. Since piston i9 is mechanically connected by racks 2iand 32 with piston 3d, piston 30 must move to the right. Bypass 36permits air to enter in front of piston 33 which acts as a bufier ordashpot. B proper proportioning of the size of bypass 35 and thestrength of the spring of spring-loaded check valve 33, the amount ofprecharging of cylinder 33 can be controlled whereby the motion ofpiston l9 can be controlled exactly by the pressure acting on piston 33.It is therefore possible to accelerate the operating mechanism at anyreasonable rate and then by precharging cylinder 33, bring the mechanismto a stop without damaging or overstressing the parts. When the circuitbreaker has attained its of said contacts. the rotary motion of saidshaft extending through an angular travel of more than 180 degrees, saidarm and link comprising a'toggle which at each limiting position of saidshaft is in an overcenter position for holding said one of saidrelatively movable contacts in the open and the closed positionsrespectively,

3. In combination with an electric circuit breaker comprising a pair ofrelatively movable contacts, an operating mechanism for producingrelative movement of said contacts comprising a force applying memberadapted to have a substantially rectilinear motion, a rotatable shaft,mean-s for translating the rectilinear motion of said force applyingmember into rotary motion of said shaft, means including an arm on saidshaft and a link connected to said arm for translating the rotary motionof said shaft into substantially rectilinear motion of one of saidcontacts, the rotary motion of said shaft extending through anangulartravel of more than 180 degrees, said arm and link comprising atoggle which at each limiting position of said shaft is in an overcenterposition for holding said one of said relatively movable contacts in theopen and the closed positions respectively, and means COoperating withsaid arm and said link for retarding both the rectilinearly androtatably moving masses.

4. In combination with an electric circuit breaker comprising a pair ofrelatively movable contacts, a source of fluid under pressure, meanscenter position for holding said one of said relatively movable contactsin the open and the closed positions respectively, the holding eifectofsaid toggle-being released upon initial movement of said force applyingmember prior to relative movement of said contacts, a source of fluidunder pressure, means including a. blast valve for supplying a blast offluid under pressure from said source adjacent said relatively movablecontacts during a circuit opening operation of said circuit breaker, andmeans rotatable with said shaft to open said blast valve while theholding effect of said toggle is released preceding relative separationof said contacts.

6. In combination with an electric circuit breaker comprising a pair ofrelatively movable contacts, a tank containing fluid under pressure,means including a blast valve for supplying a blast of fluid from saidtank adjacent said relatively movable contacts during a circuit openingoperation, an operating mechanism for producing relative movement ofsaid contacts comprisinga fluid motor connected to said source includinga piston, a shaft rotatable in response to movement of said piston meansfor interconnecting said shaft and one of said contacts, meansformanually applying a force to rotate said shaft, and means for preventinga manual force from being applied to said shaft unless substantially nofluid under pressure is present in said tank.

including a blast valve for supplying a blast of fluid adjacent saidrelatively movable contacts, an operating mechanism for producingrelative movement of said contacts comprising a force applying memberadapted to have a substantially rectilinear motion, a rotatable shaftmeans for translating the rectilinear motion of said force applyingmember into rotary motion of said shaft, means for translating therotary motion of said shaft into substantially rectilinear motion of oneof said contacts, the rotary motion of said shaft extending through anangular travel of more than 180 degrees, said last mentioned meanscomprising a toggle which at each limiting position of said shaft is inan overcenter position for holding said one of said relatively movablecontacts in the open and the closed positions respectively, and meansrotatable with said shaft to operate said blast valve.

5. In combination with an electric circuit breaker comprising a pairofrelatively movable contacts, an operating mechanism for producingrelative movement of said contacts comprising a force applying memberadapted to have a substantially rectilinear motion, a rotatable shaft,means for translating the rectilinear motion of said force applyingmember into rotary motion 7. In combination with an electric circuitbreaker comprisin a pair of relatively movable contacts, a tankcontaining fluid under pressure, an operating mechanism for producingrelative movement of said contacts comprising a fluid motor connected tosaid source, means for manof said shaft, means for translating therotary no motion of said shaft into substantially rectilinear motion ofone of said contacts, the rotary motion of said shaft extending throughan angular travel of more than 180 degrees, said last mentioned meanscomprising a toggle which at each limiting position of said shaft is inan overually applying a force to move said contacts, and means forrendering said last mentioned means ineffective to move said contactsunless substantially no fluid under pressure is present in said tank.

8. In combination with an electric circuit breaker comprising a pair ofrelatively movable contacts, a tank containing a fluid under pressure,an operating mechanism for producing relative movement of said contactscomprising a fluid motor connected tosaid source, means for manuallyapplying a force to produce relative movement of said contacts, ablow-down cock on said tank, and means for rendering said last mentionedmeans ineffective unless said blowdown cock is in the open position.

ALEXANDER C. BOISSEAU. RALPH E. BOLD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Baker et a1. Nov. 21, 1944

